Vapor recovery pumps are employed in many commercial and industrial environments to draw gaseous-state fluids away from a first, source location to a second, destination location. One location where vapor recovery pumps are used is at a gasoline station. Here, vapor recovery pumps are used to recover the vaporized petroleum products discharged as an inevitable result of the filling of a vehicle's tank. FIG. 1 schematically shows a vapor recovery system 10 for preventing the loss of volatile, flammable vapor while delivering the fuel (e.g. gasoline, kerosene, or alcohol) F to the fill port FP of a powered vehicle PV. The system 10 includes a pump and meter unit P/M for pumping fuel from a storage tank ST (typically an underground storage tank) through a metering assembly (not shown) into a dual-line passage fuel/vapor hose 12. The hand held fuel controller C has a manually actuated fuel flow trigger T attached to the end of the hose controlling the discharge of the fuel from a fuel outlet N that is insertable into the vehicle fuel port FP.
Associated with the nozzle N and insertable therewith into the fuel port FP is a vapor pick up, schematically indicated at VPU. Vapor pick up VPU connects through a vapor return conduit 13 which extends through the center of hose 12. Vapor return conduit 13 is connected to a vapor recovery pump 11. This pump 11 may be located as shown near the top of the pump meter unit P/M or located near ground level adjacent the storage tank ST. Pump 11 draws a vacuum at vapor pick up VPU so as to draw vapor from the nozzle at the VPU port and return it back to the storage tank ST through return conduit 14. The system 10 is thus used to feed fuel from the storage tank ST while simultaneously recovering volatile vapors V and returning same to the storage tank ST or other storage container. System 10 thus prevents the release of such volatile vapors into the atmosphere. The capturing of these hydrocarbon vapors also allows them to be returned to the storage tank so that they can be used as fuel. Thus, vapor recovery systems both minimize pollution and prevent the needless loss of vaporized fuel.
In some preferred forms of the vapor recovery system 10, it is desirable to provide an electrically actuated pump 11 for drawing requisite suction. Electrical pumps are often used in vapor recovery systems because they can be controlled to operate independently of the rate at which the fuel F is discharged by the system 10.
A prior art vapor pump 11 suitable for providing the requisite suction is now described in briefly with respect to FIGS. 2 and 3. This pump is the vapor recovery pump marketed by Blackmer of Grand Rapids, Mich. as Model No. VRG 3/4. Pump 11 includes a motor 22 and a pump unit 24 which are assembled as a single unit. The motor 22, located inside a motor housing 26, provides the motive force needed to draw the desired suction. Pump unit 24 includes a sleeve-like cylinder 28 which defines a pumping chamber 30 in which the actual vacuum is formed. A motor rotor 32 has a shaft 34 which is driven by the stator of the motor 22 and a pump rotor 36 integrally attached thereto which is disposed inside the pumping chamber 30. Relative to the pump chamber 30, pump rotor 36 is mounted in an off-center position. Vanes, not illustrated, are fitted into slots defined in the pump rotor 36 so as to move laterally towards and away from the center axes of the motor rotor 32 during the rotation of the rotor. The vanes cooperate with the inner wall of cylinder 28 to define small vacuum chambers into which the vapor is drawn into the pump and then is exhausted therefrom.
Pumps, such as pump 11, have proved useful devices for drawing volatile fluids, such as gasoline, away from one location to a second, storage location. Nevertheless, there are several limitations associated with current pumps. Some of these limitations are associated with the fact that it has become increasingly desirable to design these pumps so that the motor 22 and pump unit 24 are, what are referred to as "explosion proof." Here, "explosion proof" means that if inside one of these units any flammable material is some how ignited, that the flames generated by the ignition will not travel outside of the unit where it could cause other flammable material to ignite. "Explosion proof" also means that if there is ignition of flammable material inside the unit, that there will be an exhaust path for the gases generated as a result of the combustion. Providing this exhaust path prevents pressure inside the unit from building up to the point where the unit will physically explode.
Moreover, in addition to making both the motor and pump unit of a vapor recovery pump explosion proof, there is an interest in positioning these units so that they are spaced a significant distance apart. This separation is desirable for preventing damage to either the motor or pump unit from causing a chain explosion of the complementary unit. Thus, in some countries, there is now a requirement that the motor and pump be spaced at least 10 mm apart.
To date, however, it has proven a difficult task to construct a vapor recovery pump with explosion proof motor and pump unit that are spaced apart from each other and that is further configured so that the pump is relatively small in size. Size is a factor in the design of these pumps because they are often located in spaces, such as in gasoline pumps, where the space to position such sub-assemblies is limited. Moreover, in the event the use of such pumps because mandatory, they must fit in the space occupied by current pumps which typically are not large in size.
Still another cause for concern associated with current vapor recovery pumps is associated with the sensors employed to motor the state of the motor. These sensors, magnetically-sensitive Hall effect sensors, have to be positioned precisely in the motor in order to monitor the state of the motor's rotor. Problems arise because during manufacture, the rotor may be positioned too far from the sensors for them to properly function. In other instances, the motor rotors have been fitted so that they physically abut and sometimes damage the sensor. Either manufacturing misalignment may result in a rotor that may not function properly. Thus, it has proven difficult to consistently manufacture these motors so that they have the proper spacing between their rotors and their associated Hall effect sensors.
Moreover, it has become increasingly desirable to provide vapor recovery pumps used to recover volatile substances with flame arrestors. A flame arrestor is a porous member formed out of nonflammable, thermally conductive material. The flame arrestors are located along the fluid path the vapor travels both in and out of the pump. In the event the vapor in the line extending to the pump ignites, the flame arrestors serves as heat sinks that prevent the flame from traveling downline to the location where the recovered vapors are stored. Moreover, in the event the vapor in the pump unit is ignited, the flame arrestors prevent the flame in the pump chamber from propagating.
Currently, vapor recovery pumps are designed so that flame arrestors are located in the pump head, one before and one immediately downstream of the pump chamber. A disadvantage of this arrangement is that over time the dust and particulate matter that is inevitably drawn into the pump clogs the flame arrestor. Once this occurs, the pump functions either inefficiently or, not at all. Therefore, in order to ensure the efficient operation of the pump, these flame arrestors are periodically cleaned or replaced. Problems arise because these flame arrestors are located so deep into the body of the pump head that, to access them for removal or installation when the pump is part of a gasoline pump becomes a difficult, time consuming task.